Saving a Series of Debugging Runs as Checkpoints

If you save a debugging run without specifying a file name, dbx writes
the information to a special save-file. Each time you save, dbx overwrites
this save-file. However, by giving the save command a filename argument, you can save a debugging run to a file that
you can restore later, even if you have saved other debugging runs since the
one saved to filename.

Saving a series of
runs gives you a set of checkpoints, each one starting
farther back in the session. You can restore any one of these saved runs,
continue, then reset dbx to the program location and state
saved in an earlier run.